Electrolytic deposition of copper from acid solutions



iTED Tara FRANZ EDWARD srunr, oFfLonDon, ENGLAND.

:ELEo'r'RoLY'rIc DEPOSITION or corrnn r'RoM horn sonurnrons.

No Drawing.

To all whom it may concern:

Be it known that I, FRANZ EDWARD STUDT,

. a subject of. the King of Great Britain, and

a resident of London, England, have invented certain new and useful Improvements in the Electrolytic Deposltlon of Copper from Acid Solutions, of which the fol.- lowing is a specification.

This invention relates to improvements in and connected with the electrolytic deposi tion of copper from acid solutions, and has for its object the provision of a more eflicient and economic process than .those'hitherto proposed for the commercial recovery ,of copper from acid solutions or electrolytes, when these contain. a comparatively large amount of iron. r

The invention, is particularly applicable to electTO-lcflChiIlg processes in which copper ores are leached by means of acld liquors and the copper subsequently recovered from the liquors by electrolysis, as described in my prior U. S. Patent 1,260,380.

During the electrolysis, I pass into the anode'compartment, a'slow stream of gas containing S0 which gas may be produced as a byproduct, by methods described below. This is used as a depolarizer, and the following reactions take place (electrolysis) CuSO :Cu-[SO or V I acidfor use as a leaching agent in copper extraction; from the ores. 7

it has been found in such processes there islproduced an excess of sulfuric acid beyond that required for leaching purposes and my invention mainly consists inutilizing'this excess acid as a sourceof obtaining sulfur dioxid for use in the process. The invention further comprises the decomposition of some of the sulfates which remain in the solution for still further adding to;

the amount of SO, recoverable. 9 1' 7 That 1s to say according to the present invention, I proposetofprovide some vof the sulfur 'dioxid gas by takingthe excess acid liquor from the electrolytic depositing tanks;

ear oseica Specification of Letters Patent. fatenfigd 1'7, 1 921 i i 7 Application filed August 14, 1917, lSerialNdflSGJSi I fur-dioxid gas according to the well-known equations: v 7

an so gszen o geso;

- In practical working, the liquor. to be treated is runoff to, the concentration plant,

whe'refit passes through a; heated series of leaden and" acid-proof iron pans by which. the water is gradually driven off, the concen-.

trated liquor is then treated with lump sul- -fur, for instance,-at a temperature of about 600? F; when the reaction QH SO I-S: 2H O+3SO takesplace. The SO obtained is then purified, dried and liquefied according to well known processes. 1 r

The amount of new sulfur used the process is bymeans of the foregoing very considerably reduced. There is a further advantage due to the fact, that about 24% (per centum) of the total SO7 used can be absorbed by the electrolyte direct bypassing. the SQ, gas from the recovery: plant;

through a'small-absorption towerf-through which the electrolyte travels on its way from the: leaching tanks to the depositing plant. U.

By means of the foregoing a considerable I proportion of the 50, required. for the electrolytic process can be obtained from what would otherwise be waste liquors and the; balance can be obtained from burner gases 1 or by any other suitable process. Tt may be here mentioned. that while I-am primarily concerned with the obtaining of S0 from the free H and added sulfur, the-total amount of S0 obtained may be appreciably increased by the decomposition of some of the sulfates which remain'in solution.

reduced to ferrous sulfate.

per obtained there is 1.5 pound of new H 80 madefrom S0 by anodic oxidatlon.

-Owing, however, to the presence of ferric compounds present in the ore to be leached the resulting ferric sulfate also oxidizes some of the S0 to H 80 while being itself Hence, in general, when theprocess is properly carried out, there will be more than 1% pounds of new H SO made per pound of copper produced'an'dexperiments indicatethat it may be as much as 1% pounds of new acid per pound of Cu but the exact amount will depend on the type of ore being treated and the particular details of the various operations.

The amount of irrecoverable or lost acid, 71. e. thatused up by bases, other than copper, in the ore will also vary with the different types and grades of" ore but the experimental results seem to show that. it will seldom exceed the amount of new acid made and in most cases of ores amenable to successful treatmentby this process, will never equal the amount of new acid made so that therewill be a continuous excess of this new acid productlon over and above the amount of'lost acid consumed in the formation of sulfates other than GuSO v The lost acid mentioned above goes to 7 form sulfates of the various bases present in'the ore other than copp er, and it is probable that some of these sulfates can be economically treated for the recovery of their SO according to reaction such as the following:

- etFeSO,-]-S:5SO +2F2 O 2Al(SO,),,-|3S:9,SO,+2A1,O

In such case it'is probable thatpthe extra SO required when lost acid is greater than usual, wvould be generated from'sulfates-instead of by burning sulfur and so considerably reduce the total amount of sulfur required for carryingout the electroleaching process-by this method.

is subsequently used for leaching and the remainder is used for the production of some or all of the sulfur dioxid gas. 7

What I claim and desire to secure by ,Letters Patent is:

1. In the electrolysis of acid copper-sulfate solutions, the cyclic operation of preventing anodic polarization in a copperdepositing cell by introducing anamount of sulfur dioxid into the solution at the anode, capable of forming sulfuric acid in the solution in excess of that required for leaching the ores; utilizing a portion'ofthe soformed sulfuric acid for leaching copper ore material conveying the solution to'said cell, and decomposing another portion of said sulfuric acid by heating the same with a metalloid reducingagent to produce sulfur dioxid and conveying the same to the said cell for use in the first mentioned step of the process, substantially as hereinabove described.

. 2. 'A process for the recovery of copper which comprises subjecting an acid leaching solution containing copper toelectrolysis, while introducing sulfur dioxid gas directlyninto the electrolyticvessel in the vicinity of the anode, and subsequently utilizing one part of the acid exit liquor from the electrolytic vessel for leaching copper containing ore material, and utilizing another portion of the said acid exit liquor for the production'of sulfur dioxid gas for use in the electrolytic 'vessel by concentrating-the said acid liquor and heating the concentrate with ya metalloid reducing agent capable of producing sulfur dioxid therefrom.

'3. A process for therecovery of copper which comprises subjecting an acid leaching solution containing dissolved copper and containing sulfates, to electrolysis in the presence of sulfur dioxid introduced directly into the electrolytic vessel in proximity to the anode, and subsequentlyutiliz ing one portion of the acid exit liquors from the electrolytic vessel containlng' sulfates for leaching copper containing ore material and utilizing another portion of ,said

liquors for the production of sulfur dioxid gas for use in the electrolytic vessel, by coni centrating said liquor and heating the sulfuric acid and sulfates contained therein with a metalloid reducing agent capable of producing sulfur dioxid, v V 4:. In the process of the above claims, the step of heating the SO,containing material with sulfur as the metalloid reducing agent, whereby the sulfur from the SO; radical and sulfur of the reducing agent are both converted into sulfur dioxid. I In testimony whereof I afix my signature;

FRANZ EDl/VARD STUDT; 7 

